JP2019065633A - Earthquake design method of shaft - Google Patents

Abstract

To provide an earthquake design method of a shaft capable of rationally performing seismic design on a shaft having a defect portion in a shaft body planned to be built in the ground.SOLUTION: An earthquake design method for a shaft for constructing a shaft having a defect portion in a shaft body in the ground has a step of modeling in two dimensions as a vertical beam having equivalent rigidity in the vertical direction of the shaft body, and calculating an earthquake response value, a step of estimating the shear capacity of the shaft body, and a step of evaluating the aseismatic performance by comparing the estimated shear resistance with the response value. The shear strength of the shaft body is estimated based on the reduction rate preset according to the aperture rate calculated based on the elevation of the shaft body projected on the short side of the shaft body and the maximum length in the direction parallel to the short side at the defect portion, and the shear strength of the entire cross section in plan view with no defect portion in the shaft body.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a seismic design method of a shaft for constructing a shaft having a defect in the shaft body in the ground.

  Conventionally, when aseismatic design is performed to construct a cylindrical vertical shaft which is an underground structure, the vertical shaft body is modeled in two dimensions as described in, for example, Patent Document 1, and the response displacement method or 2 After confirming the seismic response by dimensional FEM analysis, the seismic performance is checked, and a method is used to determine the members so that the response value such as cross sectional force generated in the shaft becomes less than the tolerance of the shaft. ing.

JP 2008-133595 A

  However, when there is a defect in the shaft main body, a control method has not been established to check the seismic performance. At present, when confirming the response of the shaft main body, a portion having a defect (a range of 45 degrees in a radial direction from the axis of the shaft main body including the defect when viewing the shaft main body from a plan view cross section) The response value is calculated only in the part where there is no defect which is regarded and excluded. Then, the shear resistance of the portion having the defect portion is determined so as to exceed this response value.

  For this reason, it is difficult to rationally design a portion having a defect in the shaft main body, and in the reinforcement structure around the defect, the thickness of the member becomes excessively large or the shear reinforcement becomes over-dense rebar. The structure was inferior to the economy.

  In addition, when the defect portion is provided opposite to the same depth to the shaft main body, as described above, the portion having the defect portion is considered as a member to which the external force is not transmitted and excluded, so it resists shear force if it is modeled. There will be no site. For this reason, in order to set up a tunnel so as to penetrate the shaft, if it is attempted to provide an opening at the same depth as the junction with the tunnel with respect to the shaft, the current seismic design method can cope with it. There is no choice but to take measures such as changing the depth of the tunnel to be connected to the shaft.

  The present invention has been made in view of such problems, and the main object of the present invention is to make it possible to rationally design a shaft having a defect portion in a shaft main body planned to be built in the ground. It is to provide an earthquake design method.

  In order to achieve the above object, the seismic design method of a shaft of the present invention is a seismic design method of a shaft for constructing a shaft having a defect portion in the shaft body in the ground, wherein the vertical of the shaft body is vertical. Modeling in two dimensions as a vertical beam with equivalent rigidity, and calculating the response value at the time of earthquake, calculating the shear strength of the shaft body, and the estimated shear strength and the response Evaluating the aseismatic performance by comparing the values with each other, and the shear resistance of the shaft main body is determined by the short side of the shaft main body and the defect on an elevation view of the shaft main body projected. The aperture ratio is calculated based on the maximum length in the direction parallel to the short side, and the reduction ratio set in advance corresponding to the aperture ratio, and the entire plan view cross section in a state where there is no defect in the shaft main body Based on the shear strength of the Characterized in that it.

  Further, in the earthquake designing method of a shaft according to the present invention, the reduction ratio is a ratio of a shear strength in a state having the defect portion to a state without the defect portion in the shaft main body as a force resistance ratio, A plurality of aperture ratios are changed and calculated, and the characteristics are set based on the relationship between the aperture ratio and the proof stress ratio.

  According to the above-described seismic design method of the shaft, the fractured portion is provided based on the shear resistance and the reduction ratio set in advance corresponding to the aperture ratio of the entire cross section in plan view in a state where the shaft has no fractured portion. Estimate the shear strength of the shaft body.

  As a result, since it is possible to set an appropriate shear resistance according to the opening diameter of the defect portion with respect to the outer diameter of the shaft main body with respect to the shaft main body having the defect portion, it is possible to rationally design the shaft.

  Further, not only when there is only one defect but also when there are two, it is possible to secure shear resistance in the shaft main body, so the two defect parts to be provided in the shaft main body, such as so-called double-sided openings, are identical Even in the case where it is desired to be disposed opposite to the depth, it is possible to evaluate the seismic performance of the shaft body. This makes it possible to expand the linear options for tunnels to be joined to the shaft.

  According to the present invention, for a shaft having a defect portion in the shaft main body to be constructed in the ground, an appropriate shear resistance is set according to the opening diameter of the defect portion with respect to the outer diameter of the shaft body, and rational design It is possible to do

It is a flowchart of the earthquake design method of the shaft in the embodiment of the present invention. It is a figure which shows the vertical axis | shaft main body in embodiment of this invention, and a vertical direction beam model. It is a figure which shows the three-dimensional analysis model of the shaft main body in embodiment of this invention. It is a figure which shows the examination case at the time of implementing three-dimensional non-linear analysis of the shaft main body in embodiment of this invention. It is a figure which shows shear stress distribution at the time of the maximum load at the time of making a shear force act on the shaft body in embodiment of this invention. It is a figure which shows the damage condition of concrete at the time of applying a shear force to the shaft main body in embodiment of this invention. It is a figure which shows the yield condition of the shear reinforcing bar at the time of applying a shear force to the shaft main body in embodiment of this invention. It is a figure which shows the analysis model at the time of changing the magnitude | size of the defect | deletion part with respect to the outer diameter of the shaft main body in embodiment of this invention to four steps. It is a figure which shows the relationship between the opening ratio at the time of implementing three-dimensional non-linear analysis of the shaft main body in embodiment of this invention in examination case 1 (reference case), and a proof stress ratio. It is a figure which shows the relationship between the opening ratio at the time of implementing three-dimensional non-linear analysis of the shaft main body in embodiment of this invention by examination case 1-5, and a proof stress ratio.

  The seismic design method of a shaft of the present invention is a design method suitable for constructing a shaft having a defect in the shaft body in the ground. The procedure is to evaluate the seismic performance by carrying out a structural analysis in the horizontal direction of the shaft body after conducting structural analysis and checking the seismic performance in the vertical direction of the shaft body as in the conventional design method. Although present, the present invention is a method characterized by a check method of seismic performance.

  In the following, according to the flow of the flow chart shown in FIG. 1, the method of designing the shaft during earthquake will be described in detail with reference to FIGS.

  As shown in FIG. 2 (a), the vertical shaft 1 is a reinforced concrete underground structure constructed so as to extend a vertical shaft body 2 consisting of a cylindrical body with a circular cross-section in the vertical direction in the ground. It is used for starting or reaching shaft, frame of underground station building, shaft connecting to cave and so on.

  Further, in the vicinity of the lower end portion of the shaft main body 2, two defected portions 3 are provided so as to face each other at the same depth. These defects 3 are formed in a circular hole-like closed opening, and a junction with a linear underground structure extending laterally in the ground, such as a tunnel, a sewage pipe, a power line or a tunnel of a communication line. Act as.

<STEP 1: Vertical structural analysis of shaft body>
In order to carry out structural analysis in the vertical direction of the shaft body 2 of the shaft 1 described above, first, design conditions of the shaft body 2 (for example, member thickness of the shaft body 2, reinforcement, concrete compressive strength, defect 3 Set the size and position of

  Next, the shaft body 2 is modeled in two dimensions, and assuming that the shaft body 2 has no defect 3, the response value by the response displacement method or two-dimensional FEM analysis etc. Calculate the cross-sectional force (bending moment, shear).

  In the present embodiment, in modeling the shaft body 2 in two dimensions, as shown in FIG. 2 (b), modeling is carried out as a beam in which a plurality of beam elements having overall equivalent stiffness are made continuous in the vertical direction. ing. Generally, the rigidity determined by the wall of the vertical shaft body 2 per unit width is adopted as the rigidity set at this time, but in the present embodiment, a plan view cross section of the vertical shaft body 2 as shown in FIG. Set to overall stiffness.

  2 (b) and 2 (c), the rigidity of the entire cross section in plan view in which the defect portion 3 such as the AA cross section does not exist is BB The rigidity of the cross section is set, and it is assumed that there is no defect 3 in the model of the shaft main body 2.

  The response value calculated using such a vertical direction beam model is the response value of the entire plane view cross section of the vertical shaft 2 in the state without the defective portion 3, but check the seismic performance check in <STEP 3> described later. As the allowable value used when performing this, the allowable value of the entire planar view cross section of the shaft main body 2 in consideration of the influence of the defect portion 3 is used.

  Therefore, in <STEP 2>, among the allowable values of the shaft main body 2, a method of calculating the shear resistance Vd 'of the entire cross section in plan view will be described.

<Step 2: Estimation of Shear Strength Vd 'of Shaft Main Body>
In order to estimate the shear strength Vd 'of the shaft body 2 having the defect portion 3, first, as shown in FIG. 2 (d), from the elevation view of the shaft body 2 projected in the vertical direction, It calculates the maximum length r ₁ of the parallel direction of the defect portion 3 in the short side r ₁ of the short side r ₀ Toko. Based on the short side r ₀ of shafts body 2 and the maximum length r ₁ of the defect 3, calculates the opening ratio R from equation (1).
R = r ₁ / r ₀ (1)
r ₀ : short side on elevation view of shaft body 2
r ₁ : maximum length of defect 3 in the direction parallel to short side r ₀

In the present embodiment, since the shaft main body 2 is a cylindrical body having a circular cross section and the defect portion 3 is circular, the outer diameter of the shaft main body 2 is the short side r of the shaft main body 2 on the elevation view corresponds to _0, the opening diameter of the defect portion 3 corresponds to the maximum length r ₁ of the defect 3. In addition, Formula (1) is a case where there are two defects 3 in the shaft main body 2, and when there is only one defect 3, it is sufficient to divide the opening ratio R of Equation (1) by 2 .

Next, the shear resistance Vd of the whole plane view cross section in the state where there is no fracture portion 3 in the shaft main body 2 is calculated (see Formula (2)).
Vd = Vc + Vs (2)
Vd: Shear strength of shaft 2 without defect 3
Vc: Shear force of concrete
Vs: Shear force received by shear reinforcement

In addition, the shear resistance Vd of the entire plan view cross section in the state without the defective portion 3 is multiplied by the reduction ratio D set in advance corresponding to the opening ratio R. The calculated value thus calculated is estimated as the shear resistance Vd ′ of the shaft main body 2 having the defect portion 3 (see Equation (3)).
Vd '= D × Vd (3)
Vd ': Shear strength of shaft with defect
D: Reduction rate set corresponding to the aperture ratio R

The reduction rate D is a quantity set corresponding to the opening rate R, and the shear strength Vd ′ of the shaft main body 2 having the deficient portion 3 with respect to the shear resistance Vd of the entire cross section in a plan view without the deficient portion 3 It can obtain | require by Numerical formula (4) derived from the relationship between the proof stress ratio (Vd '/ Vd) which is ratio of, and the aperture ratio R. FIG. The method of calculating the reduction rate D will be described later.
D = α (1-R) + β (4)
α, β: Parameters for evaluating shear resistance

<Step 3: Seismic performance check>
After that, as in the seismic design method for a shaft conventionally implemented as a seismic performance check, the response value calculated in <STEP 1> and the allowable value of the shaft 2 are compared for each of the bending moment and the shear force. At this time, in the present embodiment, since the shaft body 2 is modeled as a beam in which a plurality of beam elements are made continuous in the vertical direction, in the seismic performance check of shear force, the response value generated in each beam element Check the cross-sectional force and the shear resistance which is the allowable value.

  And when checking with respect to the beam element of the height position in which the defect | deletion part 3 is provided among the beam elements which continue in a perpendicular direction, shear resistance Vd 'estimated by <STEP2> is employ | adopted as a tolerance.

  If the above seismic performance check determines that the safety and function of the shaft 2 can not be maintained after an earthquake, the process returns to the process of setting the design conditions of the shaft 2 and the design conditions are changed as needed. Repeat the examination of. On the other hand, when it is determined that the safety and function as the shaft 2 can be maintained, structural analysis in the horizontal direction of the shaft body 2 is performed.

<STEP 4 and 5: Horizontal structural analysis and seismic performance check>
The structural analysis in the horizontal direction and verification of seismic performance in the shaft main body 2 may be carried out according to the same procedure as the conventional seismic design method, and the general part where the defect 3 does not exist in the shaft main body 2 and the defect For each of the openings where the unit 3 is located, frame analysis is performed in two dimensions to calculate a cross-sectional force which is a response value.

  After that, as the seismic performance check, the calculated response value and the tolerance value of the shaft main body 2 are compared for each of the bending moment and the shear force. If it is determined that the safety and function as the shaft main body 2 can not be maintained in these seismic performance checks, the process returns to the process of setting the design conditions of the shaft main body 2, and the design conditions are changed as appropriate. Repeat the examination from the structural analysis of. On the other hand, when it is determined that the safety and function as the shaft main body 2 can be maintained, the shaft main body 2 is determined under the current design conditions.

  According to the above-described earthquake shaft design method of the shaft, since it is possible to set an appropriate shear resistance according to the opening ratio R to the shaft main body 2 having the defect portion 3, rational design can be performed on the shaft 1 It becomes possible.

  Further, not only when there is only one defect 3 but also when there are two, since the shear strength Vd 'can be secured in the shaft body 2, two defects such as so-called double-sided openings can be obtained with respect to the shaft body 2. Even in the case where the part 3 is to be provided opposite to the same depth, it is possible to evaluate the seismic performance of the shaft body 2. This makes it possible to expand the linear options for the tunnel to be joined to the shaft 1.

  Next, the procedure for deriving the reduction rate D and the method of calculating the optimum reduction rate D will be described in detail below.

<Method of calculating reduction rate D>
First, for the shaft 1 having the fractured portion 3 in the shaft body 2, as shown in FIG. 3, the concrete constituting the shaft body 2, the main rebar, and the distribution rebar are each modeled in three dimensions, and the behavior up to the shear failure By 3D nonlinear analysis. In the present embodiment, material non-linear finite element analysis is adopted as three-dimensional non-linear analysis.

  In carrying out this analysis, the cross-sectional shape of the shaft main body 2 is a circular cylinder, and the shape of the defect 3 is set to a circular hole-like opening, and the design conditions are as shown in the study case of FIG. did. In addition, when modeling the shaft body 2 in three dimensions, the vertical displacement of the top of the analytical model was restrained so that the bending failure did not precede, and the bottom surface was fixed.

  A three-dimensional non-linear analysis was performed to grasp the behavior up to the shear failure also for the vertical shaft 1a in a state in which there is no defect portion 3 in the vertical shaft body 2 in the same procedure as described above. 5 (a) and 5 (b), when a load acts on the vertical shaft 2 of each of the vertical shafts 1 and 1a in a direction parallel to the opening surface of the defect 3, the central position of the vertical shaft 2 and the defect 3 The shear stress distribution at the maximum load in the horizontal cross section is shown.

  In the shaft 1a where the shear stress is predominant in the shaft main body 2, in the shaft 1a in the absence of the defect portion 3 as shown in FIG. 5 (a), the defect portion 3 is distributed obliquely according to the shear deformation. In the shaft 1 having a shaft 1, it can be seen that shear stress flows obliquely to the upper side of the defect 3 and to the left and right of the defect 3 at the lower side from FIG. 5 (b).

  Further, in the vertical shaft 1a in the absence of the broken portion 3, the shear stress in the central position horizontal cross section of the broken portion 3 is large in a range parallel to the load acting direction of the vertical shaft 2 as seen in FIG. I understand how. On the other hand, in the shaft 1 having the deficient portion 3, it can be seen from FIG. 5B that the shaft 1 is enlarged in a range orthogonal to the load acting direction of the shaft body 2.

  Thus, in the shaft body 2 having the defect portion 3, the shear force is transmitted to the range orthogonal to the load acting direction of the shaft body 2 adjacent to the defect portion 3 via the vicinity of the upper portion of the defect portion 3 in the shaft body 2 It is done. Therefore, it can be said that the shear resistance can be secured in the entire shaft main body 2 even when the two defect portions 3 exist at the same depth in a state of facing the shaft main body 2.

  Next, in FIGS. 6 (a) and 6 (b), the state of damage to concrete at maximum load leading to shear failure in the shaft main body 2 is shown in FIGS. 7 (a) and (b). The damage status of the horizontal rebar at maximum load is shown respectively.

  Regarding the damage condition of the concrete, in the shaft 1a in the state where there is no defect portion 3, looking at FIG. 6 (a), the entire shaft body 2 is sheared and deformed. On the other hand, in the shaft 1 having the deficient portion 3, it can be seen from FIG. 6 (b) that deformation concentrates in the vicinity of the deficient portion 3 and causes compression and softening of concrete around the deficient portion 3.

  Further, regarding the damage state of the shear reinforcing bars, in the shaft 1a in the state without the defect portion 3, looking at FIG. 7A, the yield range is distributed diagonally in the entire shaft body 2 according to the shear deformation. On the other hand, in the shaft 1 having the defect portion 3, it can be seen from FIG. 7B that a distribution of a yield range corresponding to the shear deformation is generated in the vicinity of the defect portion 3.

  As a result, the shaft main body 2 of the shaft 1 having the defect portion 3 is a shaft main body 2 of the shaft 1 a in a state without the defect portion 3 due to concentration of shear deformation around the defect portion 3 where the concrete and rebar are deficient. It can be said that the shear resistance Vd 'is lowered compared to the above.

Next, in order to understand the relationship between the opening ratio R and the shear resistance Vd ′, the shaft 1 having the defect portion 3 in the shaft main body 2 is described above as shown in FIGS. 8 (a) to 8 (d). Four shafts 1 having different opening ratios R, in which the opening diameter of the defect 3 was changed to four stages corresponding to the maximum length r ₁ of the defect 3 were prepared. Then, with respect to the vertical shaft 1a in a state without these and the defect portion 3, the behavior up to the shear failure is grasped by the three-dimensional non-linear analysis in the same procedure as above, and the maximum load leading to the shear fracture in the load displacement relationship is grasped Do.

  In the present embodiment, this maximum load is treated as shear resistance Vd 'and Vd, and the result is shown in FIG. 9 with the opening ratio R on the horizontal axis and the proof ratio (Vd' / Vd) on the vertical axis. It was plotted on the graph taken.

  Looking at the graph in FIG. 9, the proof stress ratio (Vd '/ Vd) decreases as the aperture ratio R increases, and a linear relationship between the aperture ratio R and the proof stress ratio (Vd' / Vd) is observed be able to. Therefore, the resistance ratio (Vd '/ Vd) is expressed by a linear function based on the aperture ratio R, and this is defined as the reduction ratio D (see (4) above). Thereby, the reduction rate D corresponding to the aperture ratio R can be calculated by substituting the quantity corresponding to the aperture ratio R into the equation (4) as appropriate.

  The inventors also found that, in the shaft body 2 having the defect portion 3, the shear resistance Vd 'is at least affected by the member thickness of the shaft body 2, the shear reinforcement ratio, the compressive strength of concrete, and the number of openings. You are getting Therefore, prepare an analysis model of shaft body 2 with design conditions changed appropriately for these four points, and carry out three-dimensional non-linear analysis in the same procedure as above, and grasp shear resistance Vd 'from the maximum load leading to shear failure The results are plotted in the graph shown in FIG.

  Specifically, for each of the four types of shafts 1 shown in FIGS. 8A to 8D, a three-dimensional non-linear analysis was performed under eight design conditions up to examination cases 1 to 5 in FIG. Each study case is based on case 1, cases 2-1 and 2-2 are member thickness, cases 3-1 and 3-2 are shear reinforcement ratio, and case 4-1 and 4-2 are compressive strength of concrete I changed each.

  Moreover, Case 5 has the same member thickness, shear reinforcement ratio, and concrete strength as Case 1 as a reference, but has only one defective portion 3. In addition, in order to calculate a proof stress ratio (Vd '/ Vd) in all the above-mentioned design conditions, the shear proof stress Vd is calculated also about the shaft main body 2 which assumed that there is no defect part 3.

  It can be seen from the graph of FIG. 10 that there is a substantially linear relationship between the aperture ratio R and the proof stress ratio (Vd ′ / Vd) in any of the cases 2 to 5. In addition, since cases 2 to 5 have different inclinations with respect to case 1 of the standard, the member thickness of the shaft main body 2, the shear reinforcement ratio, the compressive strength of concrete, and the number of defective portions 3 each have a proof stress ratio. It can also be confirmed that it affects (Vd '/ Vd). Furthermore, among Cases 2 to 4, in Case 3-1 and Case 3-2, in which the quantity of shear reinforcement ratio is changed, the difference in linear inclination appears remarkably, and the shear reinforcement ratio is the proof stress ratio (Vd It can be seen that the '/ Vd) is greatly affected.

  Therefore, when setting the reduction rate D, the parameter α according to the member thickness of the shaft main body 2 in the shaft 1 to be constructed, the shear reinforcement ratio, the compressive strength of concrete, the number of defects 3 etc. And β (see equation (4) above) may be adjusted as appropriate, and the optimum reduction rate D may be set according to the design conditions of the shaft 2. Although any adjustment method of α and β may be used, for example, with α or β as the objective variable, the member thickness of the shaft main body 2, shear reinforcement ratio, the compressive strength of concrete, and the number of defects 3 as the explanatory variables It is also conceivable to set the reduction rate D by performing multiple regression analysis.

  Thus, in calculating the shear resistance Vd 'of the shaft main body 2 using the equations (3) and (4), the member thickness of the shaft main body 2 to be constructed, the shear reinforcement ratio, the compressive strength of concrete, and the loss portion 3 By using the optimal reduction rate D according to the design conditions of the shaft 2 such as the number, it becomes possible to design the shaft 1 more rationally.

  In the present embodiment, the member thickness of the shaft main body 2 used in the cases 2-1 and 2-2 includes the member thickness (1.0 to 2.5 m) of the previous deep shaft, and the case 3-3 is used. The shear reinforcement ratio used in 1 and 3-2 includes the minimum and maximum values defined in the concrete standard specification. Moreover, the concrete strength used by case 4-1 and 4-2 considers the application of high strength concrete, and sets the examination case each.

  Therefore, in the graph of FIG. 10, the line showing the relationship between the aperture ratio R and the proof stress ratio (Vd '/ Vd) is located at a position including all the plots of Cases 1 to 5, that is, below the plots. And α are determined, and the reduction rate D is set. In this way, it is possible to set the shear resistance Vd 'on the safe side at least with respect to the member thickness of the shaft body 2, the shear reinforcing bar ratio, the compressive strength of concrete, and the number of defects 3.

The broken lines shown in the graph of FIG. 10 are α = 1 and β = 0, and if α and β are set in the range of at least α ≦ 1 and β ≧ 0, the shear strength Vd ′ of the shaft main body 2 having the defect portion 3 It is possible to conduct a safe seismic performance check. Incidentally, when α = 1 and β = 0 are adopted, the shear resistance Vd ′ of the shaft main body 2 having the defect portion 3 is calculated by the following equation (5) from the equation (3) and the equation (4). It can be estimated by substituting.
Vd '= (1-R) x Vd (5)

In the conventional seismic design method, when calculating the shear resistance Vd ′ of the shaft main body 2 having one defect portion 3, the above-mentioned equation (2) is applied mutatis mutandis. In this case, a portion of the shaft main body 2 where the defect portion 3 exists (a range of 45 degrees in a radial direction from the axis of the shaft main body 2 including the defect portion 3 when viewed from a plan view cross section of the shaft Do not treat b)) as a shear transfer member. For this reason, when setting the shear force Vc which has concrete reception with Numerical formula (6), the abdominal part width bw will be halved and it will calculate.
Vc = (τ _al b _w z) (6)
τ _al : Short-term allowable shear stress of concrete
b _w : Abdominal width of the member cross section
z = d / 1.15
: Distance from the point of application of total compressive stress to the centroid of the tensile bar cross section

  Then, since the number of shear forces Vc received by concrete is underestimated, if it is attempted to secure the necessary shear resistance Vd 'without changing the member thickness of the shaft main body 2, the shear force Vs received by the shear reinforcements is made large. However, the shear reinforcement bars became overconsolidated and uneconomical.

  However, in the earthquake design method of the present embodiment, since the shear loadable body Vd 'is secured in the entire shaft main body 2, the shear force Vc possessed by the concrete can be appropriately evaluated without underestimation, and comparison with the conventional seismic design method Thus, the shear force Vs received by the shear reinforcement can be reduced. This makes it possible to reduce the amount of reinforcement of the shear reinforcing bars and to make a rational and economical design.

  The seismic design method of a shaft of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the present embodiment, a cylinder is adopted for the cross-sectional shape of the vertical shaft main body 2, but the present invention is not necessarily limited to this, and any cylindrical tube etc. may be used as long as it is a cylindrical body.

  Further, the shape of the defect portion 3 is not necessarily limited to the shape of a circular hole, and may be any shape such as a horseshoe if it is closed. Furthermore, if the arrangement position of the defect portion 3 is in the vicinity of the lower end portion of the shaft main body 2, the case where one defect portion 3 is provided in the shaft main body 2 such as so-called one side opening or two defect portions 3 such as both side openings It may be either of the cases where it is provided opposite to the same depth of 2.

  In addition, in the present embodiment, although the response value of the entire planar view cross section of the shaft main body 2 in the state without the defective portion 3 is calculated in <STEP 1>, the present invention is not necessarily limited thereto. For example, the response value of the entire plan view cross section corresponding to the opening ratio R may be calculated for the shaft main body 2 having the defect portion 3 and the cross sectional force may be used for the seismic performance check of <STEP 3>.

1 shaft 1a shaft 2 shaft body 3 defect part

Claims (2)

A seismic design method for a shaft for constructing a shaft having a defect in the shaft body in the ground,
Modeling in two dimensions as a vertical beam having equivalent rigidity in the vertical direction of the shaft body, and calculating an earthquake response value;
Estimating the shear capacity of the shaft body;
Evaluating the aseismatic performance by comparing the estimated shear resistance with the response value;
The shear strength of the shaft body is calculated on the basis of the short side of the shaft body and the maximum length in the direction parallel to the short side at the defect on an elevation view of the shaft body projected. During an earthquake of the shaft, which is estimated based on the reduction ratio previously set according to the aperture ratio, and the shear resistance of the whole cross section in plan view with no defect in the shaft body. How to design. The earthquake seismic design method of a shaft according to claim 1, wherein
The reduction rate is
The ratio of the shear resistance of the state having the deficient portion to the state without the deficient portion in the shaft main body is defined as a fulcrums ratio, and the plurality of the fulcrums are calculated by changing the aperture ratio,
It is set from the relationship between the aperture ratio and the resistance ratio, and the earthquake design method of the shaft.